Solid core optic fiber and method for the production thereof

ABSTRACT

An optical insulated core with a coated optical fiber ( 2 ) shows a core jacket ( 4 ) with a core jacket material containing polyvinylchloride ( 41 ) which is applied to the coating of the optical fiber. It contains a solid component ( 42 ) distributed within the core jacket material, which produces a mechanical separation effect against the coating of the optical fiber. The solid component ( 42 ) is mixed and distributed into the core jacket material during a compounding process. Thus the core jacket can be removed from the coating of the optical fiber in a simple way.

FIELD OF THE INVENTION

The present invention concerns an optical insulated core as well as aprocess for the manufacture of such an optical insulated core.

BACKGROUND OF THE INVENTION

In order to keep optical fibers in the form of optical glass fibers freefrom outside influences, optical fibers are generally protected by ajacket. A simple possibility to protect optical fibers in the form ofglass fibers against outside influences consists of providing theoptical fiber with a coating and immediately applying a firm protectivejacket made of a suitable plastic over the coating of the optical fiber.Such an arrangement is commonly designated as an insulated core orfilled core. Such a core construction distinguishes itself by asubstantial decrease of the outer diameter of the core in contrast to aloose tube.

Especially for the installation and connectorization it is necessary toremove the core jacket of an insulated core from the optical fiber. Tomake it easier to remove a PVC core jacket, which containspolyvinylchloride, from the coating of an optical fiber, it is usual toplace a Teflon layer (so-called TB-2 coating) between the core jacketand the coating of the optical fiber as a separating layer. Thus a usercan strip the core jacket of an insulated core over a greater length inone step.

An optical insulated core thus constructed has, however, certaindisadvantages. An optical insulated core with a TB-2 layer iscomparatively more expensive to produce, especially the application ofthe different layers is comparatively costly. During application of thelayers in one work process, the danger exists for an uneven layerthickness and formation of kinks in the Teflon due to abrasion in theextruder tool. Additionally, due to voids where there is no Teflon,localized attenuation peaks can occur. Furthermore, generally only alimited pay-off speed is possible during the extrusion process. With a2-step extrusion process, where the Teflon layer is applied firstfollowed by the PVC core jacket, additional investment costs areincurred due to the necessary expansion of the extrusion lines. Handlingproblems can also be created, since the Teflon layer is commonly formedas a 3-component mixture and the components contain hazardous elements.

SUMMARY OF THE INVENTION

It is the objective of the present invention, to specify an opticalinsulated core, where the core jacket can be removed comparativelyeasily from the coating of the optical fiber while avoiding thedisadvantages listed above.

Additionally, it is the objective of the present invention, to specify aprocess for the manufacture of such an optical insulated core.

The objective of the optical insulated core is achieved with an opticalinsulated core according to patent claim 1. The objective of the processfor the manufacture of an optical insulated core is achieved with aprocess for the manufacture of an optical insulated core according topatent claim 9.

The optical insulated core according to the invention has a core jacketwith a core jacket material containing polyvinylchloride, which containsa solid distributed in the core jacket material, which produces amechanical separation effect against the coating of the optical fiber.The manufacture of the optical insulated core occurs in such a way, thatthe solid component producing the separation effect is mixed anddistributed into the matrix material forming the core jacket andcontaining polyvinylchloride by means of a compounding process.

This results in the advantage, that the manufacturing costs compared toa core construction with a Teflon separating layer are significantlyreduced, because the comparatively expensive Teflon is eliminated, theinvestment costs are minimized due to the one-step process and the timenecessary for manufacture of the insulated core is decreased. Formanufacture of the insulated core according to the invention only oneextrusion line and one extrusion process are necessary. In comparison tothe manufacture of an insulated core with a Teflon layer, the extrusionspeed during application of the PVC core jacket onto the coated opticalfiber can be significantly increased, for example from a speed of 140m/min for manufacture of an insulated core with a Teflon layer to aspeed greater than 300 m/min for the manufacture of an insulated coreaccording to the invention.

The provision of the solid component does not affect the total physicalcharacteristic profile of the PVC core jacket, since especially thestability and temperature behavior of the PVC core jacket are notaffected. Thus localized attenuation characteristics of the insulatedcore according to the invention are not affected due to the provision ofthe solid component. Thus the physical and optical characteristicsprofile of the insulated core are not negatively affected in the coreconstruction according to the invention.

In an advantageous construction sample of the invention, a siliconeelastomer is mixed into the core jacket material as a solid component.This is mixed into the matrix material of the core jacket during acompounding process, so that the solid component in the form of thesilicone elastomer is distributed in a statistically homogenous way inthe core jacket material.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 shows a cross sectional view of the fiber optic cable of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

In a preferred construction sample of the invention a high molecularpolysiloxane formulation is mixed into the core jacket material. Thisformulation has a molecular chain length greater than approximately100,000 polymerized monomers. It was especially advantageous to mix HTVsilicone rubber (high temperature-vulcanized silicone rubber) based onpolydimethylvinyl-siloxane into the core jacket material.

In a further construction sample of the invention, a component is mixedinto the core jacket material, which shows an aversion to orincompatibility with the coating of the optical fiber due to itschemical composition and thus produces the separating effect against thecoating of the optical fiber. Such a component can, for example, bechlorinated polyethylene (CPE).

In a further construction sample of the invention a mineral lubricant orseparation element, especially in the form of a high-dispersion siliconedioxide (Sipemat 44) or a talcum product is mixed into the core jacketmaterial as a filling compound element.

In another advantageous construction sample of the invention, a wax-likeseparation element, especially fatty acid esters, is mixed into the corejacket material.

Further advantageous constructions and developments of the invention aregiven in the sub-claims.

In the following, the invention is explained in more detail by means ofthe diagrams in the figures, which shows a construction form of aninsulated core according to the invention.

The figure shows a longitudinal section of an optical insulated core 1,which contains an optical fiber in the form of an optical glass fiber 2.The glass fiber 2 is coated all-around with an acrylic coating 3. Thecore jacket 4, which encloses the optical insulated core towards theoutside is applied to the coating 3. The core jacket 4 is formed by aPVC insulation compound, where the polyvinylchlorides contained in thecore jacket material are designated with the reference character 41.Additionally, an non-soluble solid component 42 is contained in the corejacket material of the core jacket, which is mixed in by a compoundingprocess during manufacture of the insulated core in such a way, that itis statistically distributed in a homogenous way within the core jacketmaterial. The solid component 42 in the form of a high-molecularpolysiloxane formulation produces a mechanical separation effect againstthe acrylic coating 3 of the optical fiber 2.

By providing the solid component 42, the ability to remove the corejacket 4 from the coating 3 of the optical fiber 2 can be noticeablyimproved. It is advantageous that the physical and opticalcharacteristics profile of the insulated core 1 are not negativelyinfluenced due to the high-molecular polysiloxane. In addition, thetotal characteristics profile of the PVC core jacket is not affected,especially in regard to stability and temperature behavior. In order toavoid negative localized attenuation increases due to the polysiloxane,the polysiloxane is highly molecular in such a way, that it does notmigrate into the layer 4.

In a further construction sample of the invention a solid component 42is mixed into the core jacket material of the core jacket 4, which showsan aversion to the acrylic coating 3 of the optical fiber 2 due to itschemical composition. Such a component is especially formed bychlorination of polyethylene.

1. An optical insulated cable with an optical fiber, which includes acoating, and a cable jacket, the cable jacket material includingpolyvinylchloride, which is applied to the coating of the optical fiber,and which includes a silicone elastomer as a solid component distributedwith the cable jacket material, that produces a mechanical separationeffect against the coating of the optical fiber, wherein the solidcomponent of the cable jacket material includes a HTV silicone rubberbased on polydimethylvinylsiloxane having a molecular chain lengthgreater than approximately 100,000 polymerized monomers.
 2. The opticalinsulated cable according to claim 1, wherein the cable jacket materialincludes a component having an aversion to the coating of the opticalfiber due to its chemical composition.
 3. The optical insulated cableaccording to claim 2, wherein the cable jacket material includes achlorinated polyethylene.
 4. The optical insulated cable according toclaim 1, wherein the cable jacket material includes a mineral lubricantor separating component.
 5. The optical insulated cable according toclaim 1, wherein the jacket cable material includes a wax-likeseparating material.
 6. A process for the manufacture of an opticalinsulated cable with an optical fiber which has a coating, where asilicone elastomer as a solid component, which produces a mechanicalseparation effect against the coating of the optical fiber, is mixed anddistributed during a compounding process into matrix material forming asolid component of the cable jacket that includes polyvinylchloride anda HTV silicone rubber based on polydimethylvinylsiloxane having amolecular chain length greater than approximately 100,000 polymerizedmonomers.